Blurry Backgrounds - Focused close objects

Hi,
No matter what I do - pictures of clouds come out as noisy as pictures on a point-and-shoot. The camera takes great pictures of close up objects, but far away things like background just don't come out right!
I bought it to take pictures of clouds, but even when there is a contrast, like a cloud and blue sky, it still comes out noisy.
I have the af-nikkor-50mm and I am shooting on Aperture mode.
Please advise?